Communications networks are used to exchange messages among several interacting, spatially-separated elements. Networks may be classified by different attributes. For example, the geographic span of the network could be over a wide area, a metropolitan area, a local area, or a personal area, and the corresponding networks would be denoted as wide area network (WAN), metropolitan area network (MAN), local area network (LAN), or personal area network (PAN). Networks also differ in the switching/routing technique used to interconnect the various network nodes and devices (e.g. circuit switching vs. packet switching), in the type of physical media employed for waveform propagation (e.g. wired vs. wireless), or in the set of communication protocols used (e.g. Internet protocol suite, SONET (Synchronous Optical Networking), Ethernet, Asynchronous Transfer Mode (ATM), etc.).
One important attribute of communications networks is the usage of wired or wireless media for signal transmission among the network constituents. For wired networks, tangible physical media such as copper wire, coaxial cable, fiber optic cable, etc. propagate guided electromagnetic waveforms which transport message traffic over a distance. Wired networks are a traditional form of communications networks and are typically favored for interconnection of fixed, high capacity network elements or for bulk data transfer. For example, fiber optic cables are often the preferred transmission media for very high throughput transport applications over long distances between large network hubs, for example, bulk data transport across or between continents over the Earth's surface.
Wireless networks, on the other hand, are often preferred when mobile elements which need dynamic connectivity are used or if the network architecture is formed in an ad hoc, rather than fixed, topology. Wireless networks employ intangible physical media in an unguided propagation mode using electromagnetic waves in the radio, microwave, infrared, optical, etc. frequency bands. Wireless networks have the distinct advantage of facilitating user mobility and rapid field deployment compared to fixed wired networks. However, wireless propagation techniques require significant active resource management among the network users and high levels of mutual coordination and cooperation for compatible spectrum utilization. One such resource management issue is the authorization of users with a specific access type.